In computer systems, many different components communicate with each other. Typically, various semiconductor devices that may be coupled on a motherboard or other circuit board may communicate along traces on the board, such as various bus lines. Furthermore, other signaling occurs between components in a first system and a second system using various input/output (I/O) circuitry. In communicating data between different devices, an offset can occur due to various conditions.
The undesired offset in receivers can be as high as ±50 millivolts (mV) depending on the transistor sizing, layout, and process mismatch coefficients. This offset degrades the voltage sensitivity of the receivers; therefore, offset cancellation techniques are often employed on the receiver circuits. A conventional approach is to use a voltage offset comparator (VOC) as the first stage in receivers and followed by a sampler. Analog VOC circuits can consume substantial current in order to accommodate the bandwidth requirements. Moreover, in multi-phase clocking input/outputs (I/Os), samplers are interleaved and each of them requires a VOC. Consequently, power consumption and logic complexity becomes prohibitive.